3 in 4 Workers Made Ill by Workplace Temperatures Say It Went Unrecorded

Among workers in temperature-exposed jobs who were made ill by heat or cold at work, 3 in 4 said at least one illness was never officially reported to or recorded by their employer. For the people inside America’s warehouses, plants, and kitchens, the building itself can be the hazard, and much of what it does to them never reaches the record.

To find where that pressure is greatest, we ranked the 100 largest U.S. metropolitan statistical areas on local weather and the share of workers in temperature-exposed indoor industries, once for winter and once for summer.

We then paired those rankings with federal injury records and a September 2026 survey of 384 American workers in temperature-exposed jobs. Among respondents, 63% worked primarily indoors, 15% split their time evenly between indoors and outdoors, 12% worked primarily outdoors, and 10% worked mostly in a vehicle, cab, or trailer.

Our findings show where difficult indoor conditions collide with limited protections, unrecorded illness, and workers who may hesitate to speak up.

Key Takeaways

• 3 in 4 workers made ill by workplace temperatures say it was never officially recorded.
  
• Grand Rapids, MI, is the hardest of the 100 largest metros for indoor winter work; Bakersfield, CA, is the hardest for indoor summer work.
  
• The 10 hardest winter metros hold 1,000,966 workers in exposed indoor industries, compared with 663,583 across the 10 hardest summer metros.
  
• Minnesota is the only state that sets a numerical indoor temperature limit for both heat and cold.
  
• 49 states have no indoor workplace cold standard, and 98% of cold-exposed indoor workers are in one of them.
  
• Two places rank in the hardest 20 metros for both winter and summer: Wichita, KS, and Greensboro, NC.
  
• 41% would hesitate to tell a supervisor that temperatures are unsafe because they believe nothing would change.
  
• 20% have skipped a break in extreme conditions for fear of losing pay or hours, and 18% have done so to avoid being seen as weak.
  

What Workers Say Happens When Temps Rise and Fall

Temperature problems at work can affect far more than comfort. The workers we surveyed described physical symptoms, slower work, mistakes, and situations in which speaking up or taking a break could have consequences.

Among surveyed workers, 87% reported at least one physical symptom on the job caused by workplace temperature. More than half (51%) said the temperature where they worked affected the quality of their work.

The effects also reached day-to-day performance: 82% had worked more slowly because of the temperature, while 52% said they had made a mistake on the job because of it.

Yet raising the issue didn't always feel worthwhile or safe. About 2 in 5 workers (41%) said they would hesitate to tell a supervisor that temperatures were unsafe because they believe nothing would change. Under extreme conditions, 20% had kept working or skipped a break out of fear of losing pay or hours, and 18% had done so to avoid being seen as weak.

Even when exposure to temperature made someone unwell, the problem could remain outside the official workplace record. Among those who had been made ill by temperature at work, 75% said at least one illness was never officially recorded.

The question asked whether they had ever had a heat-related or cold-related illness or injury at work that was never officially reported or recorded. Of those who had been made ill, 52% chose not to report it, 17% reported it but did not believe it was recorded, and 6% said someone discouraged them from reporting. Together, those make up the 3 in 4.

The Extreme Temperature Workplace Index

Weather alone doesn't determine where indoor workers face the greatest temperature pressure. The concentration of jobs in warehouses, factories, kitchens, laundries, and other exposed workplaces can change the picture considerably.

The Extreme Temperature Workplace Index ranks the 100 largest U.S. metro areas twice, once for winter and once for summer. Each seasonal ranking is based on two factors: how often the weather turns extreme and what share of local jobs are in exposed indoor industries. 

Grand Rapids, MI, ranked as the hardest of the 100 largest metros for indoor winter work, with 129 freezing days and 23% of its workforce, or 123,178 workers, in exposed jobs.

The 10 hardest winter metros accounted for 1,000,966 exposed workers, compared with 663,583 across the 10 hardest summer metros. Wichita and Greensboro also appeared among the 20 hardest in both seasons, leaving workers in those metros facing significant temperature extremes at both ends of the thermometer.

The full 20 hardest metros for indoor winter cold were:

Bakersfield, CA, ranked as the hardest of the 100 largest metros for indoor summer work, with 114 heat days and 24% of its workforce, or 51,470 workers, in exposed jobs. Stockton-Lodi, CA, ranked second with 92 heat days and 30% of workers exposed, followed by Wichita, KS, with 92 heat days and 29% of workers exposed.

California placed four metros in the hardest 20 despite being one of only five states with an indoor heat standard. Its Central Valley combined high heat with dense concentrations of warehousing and food-processing jobs, pushing Bakersfield, Stockton-Lodi, and Fresno toward the top of the ranking.

The full 20 hardest metros for indoor summer heat were:

The ranking also showed why climate alone can give an incomplete picture of indoor exposure. Only four of the summer's hardest 20 metros were among the country's 10 hottest metros, and only 12 were among the hottest 25. Miami provided the clearest example. It had the fourth-most extreme heat days of any large metro but the third-lowest share of workers in hot indoor jobs, putting it 45th in the summer index.

Indoor Heat Injuries and Gaps in Cold and Heat Standards

Federal injury records offer another view of temperature hazards inside workplaces. They also show how differently the same hazard can appear depending on the industry and on whether the work is done indoors or outdoors.

Among recorded heat injuries with a known work setting, 38% happened indoors: 1,630 cases against 2,670 outdoors across all industry divisions. The chart shows the six largest of those divisions. Manufacturing recorded 500 indoor heat cases compared with 110 outdoors, while construction showed almost the reverse pattern, with 150 indoors and 610 outdoors.

Occupational heat injury isn't limited to work performed outside. Manufacturing plus trade, transportation, and utilities accounted for 59% of all recorded heat cases, 3,110 of 5,280, compared with 16% for construction. These shares cover every recorded case, including the 980 where BLS did not specify a setting, so they are larger than the indoor and outdoor figures above.

Few States Have Indoor Cold or Heat Standards

Minnesota is the only state with an indoor workplace cold standard, requiring minimum temperatures of 65°F for light to moderate work and 60°F for heavy work. The other 49 states have no indoor cold standard, leaving 98% of cold-exposed indoor workers in states without one.

Indoor workplace heat standards are also uncommon: five states have one, while 45 don't. Those standards take different forms. Minnesota sets numerical temperature limits, while California, Oregon, Maryland, and Nevada require heat-illness prevention measures triggered by temperature or by a hazard assessment rather than capping how hot a workplace may get. Across the country, 83% of heat-exposed indoor workers are in a state with no indoor heat standard.

Employers Have Safety Duties Even Without Specific Standards

The absence of a specific indoor standard doesn't remove an employer’s safety obligations. Under the General Duty Clause of the Occupational Safety and Health Act, employers must provide a workplace free from recognized hazards likely to cause death or serious physical harm. OSHA can use this requirement to cite employers for failing to protect workers from dangerous heat.

OSHA has also proposed a heat injury and illness prevention standard covering both indoor and outdoor workplaces, but the rule hasn't been finalized. The proposed rule was published in 2024, the public comment period closed in January 2025, and hearings ran through October 2025. A supplemental proposal is targeted for December 2026.

 

When Temperature Becomes a Workplace Safety Issue

The findings pointed to a problem that stretched from the shop floor to the official record. Workers reported physical symptoms, slower work, and mistakes, while many who became ill said at least one case was never formally recorded. The metro rankings showed that serious temperature pressure wasn't confined to the hottest or coldest places, and most exposed workers were in states without indoor standards.

For safety managers, facility teams, supervisors, and workers, temperature deserves attention as a workplace condition rather than simply a seasonal inconvenience. A warehouse, production floor, or kitchen doesn't have to be outdoors to become dangerously hot or cold, and an unreported hazard can be much harder to see.

Methodology

We built the Extreme Temperature Workplace Index to rank the 100 largest U.S. metropolitan statistical areas by 2025 population on the indoor temperature pressure their workers face, once for summer and once for winter. Each season combines a weather leg and a workforce leg. Summer weather is days a year when the National Weather Service heat index reaches 90 degrees or higher, according to CDC extreme heat days. Winter weather refers to days a year when the low temperature reaches 32 degrees or lower, based on NOAA GHCN station records.

Both are 10-year averages covering 2014 to 2023, and the summer figure is complete for every metro. Station records are not, so the winter figure is the average of the years a metro's station reported, which is all 10 for 79 metros, nine for 14 metros, and eight or fewer for 7 metros.

The workforce leg is the share of local jobs in exposed indoor industries, from Census County Business Patterns 2023, covering general warehousing, all manufacturing, commercial kitchens, and industrial laundries for summer, and general warehousing, refrigerated warehousing, and all manufacturing for winter. Kitchens and laundries are summer only because they generate heat, which has no cold equivalent. County Business Patterns is used rather than the Quarterly Census of Employment and Wages because QCEW suppresses cells that County Business Patterns publishes, and 12 of the 100 metros are publishable only at the metro level.

A metro qualifies for a season only if its weather is worse than the median of the 100 metros for that season, which stops a mild-weather metro from climbing a temperature ranking on its factory count alone; 49 metros clear the summer bar, and 50 clear the winter bar. Qualifying metros are ranked on each leg against all 100 metros, the two positions are added, and the lowest total ranks first. Ties break on the raw count of exposed workers. There is no weighted score and no model. Rankings describe only the 100 metros included, so a metro named as hardest is the highest ranked among those 100 rather than among all U.S. metro areas.

Injury figures come from the Bureau of Labor Statistics Survey of Occupational Injuries and Illnesses, days-away-from-work cases for 2023 and 2024 combined. Counts are used rather than rates because the BLS publishes temperature rates to one decimal, at which resolution the heat and cold series collapse. Where a figure is described as not published, BLS withheld the estimate as unreliable rather than reporting zero. BLS specified a setting for 4,300 of the 5,280 recorded heat cases. The remaining 980 have no setting recorded, so shares of all cases are larger than the indoor and outdoor figures.

State protection is scored on whether a state has an enforceable indoor workplace heat standard, as of September 23, 2026. Five states do: California Title 8 Section 3396, Oregon OAR 437-002-0156, Maryland COMAR 09.12.32, Nevada LCB File R131-24AP, and Minnesota Rules 5205.0110. These are not the same kind of rule. Minnesota sets numerical temperature limits by workload. The other four require heat-illness prevention measures triggered by a temperature threshold or, in Nevada’s case, by a written job hazard analysis. Of the five, only Minnesota also sets a cold limit, so 45 states have no indoor heat standard, and 49 have no indoor cold standard. Washington and Colorado have heat rules that cover only outdoor and agricultural work and are counted as having no indoor coverage. New Mexico rulemaking and the 2025 Arizona executive order are pending and not counted. The national coverage figures are computed across all U.S. counties on the same industry definitions from County Business Patterns 2023. The heat figure excludes industrial laundries, which the county file does not carry.

We also surveyed 384 American workers in temperature-exposed jobs in September 2026. By work setting, 63% worked primarily indoors, 15% split evenly between indoors and outdoors, 12% primarily outdoors, and 10% mostly in a vehicle, cab, or trailer. Survey findings are reported on the full sample unless stated otherwise. The gender breakdown was men 59%, women 39%, and 2% non-binary or preferring not to answer. The generational breakdown was millennials 49%, Gen X 29%, Gen Z 17%, and baby boomers and older 5%. Only responses with a unique respondent ID were used, numeric open-ended answers had outliers removed by the interquartile range method, and Other, please specify was excluded from every select-all question.

Limitations: The index infers temperature exposure from climate and industry mix rather than measuring conditions inside any building, so it identifies where exposure is most likely, not where it is confirmed. Urban Honolulu ranks in neither season because it has no published CDC heat-day figure and no freezing days. Winston-Salem and Lakeland have the thinnest station records of the 100 metros, at six and seven years. Station data affects only the winter measure. Neither metro qualifies for the winter list, though Winston-Salem falls just 1.4 days below the qualifying median, so a fuller record could place it there. At 384 respondents, the survey supports national figures and cuts by work setting, and does not support a metro, state, region, or industry figure, so none is published. Survey findings cover temperature-exposed workers generally rather than indoor workers only. All percentages are rounded to the nearest whole number, so some sets do not total 100, and questions that allowed more than one answer are not expected to.

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